Adeleke, I. ., and A. . Ibiwoye. “Network Sampling of Hard-to-Reach Population: An Application to the Substance Abuse Problem Among Tertiary Education Students in Nigeria”. International Journal of Asian Social Science, vol. 1, no. 5, Dec. 2011, pp. 133-41, https://archive.aessweb.com/index.php/5007/article/view/2146.